Animation
CS 551 / 651
David Brogan
dbrogan@cs.virginia.edu
Introduction
We are going to study how things move and the
creation of computer graphics representations that
look “good enough”
Rendering is: mapping light sources and surfaces to a
vector of pixel colors
Animation is: mapping objects, intentions, and external
forces to a vector of new object positions / orientations
We will not
Develop drawing skills
• but we may study how others draw so we can automate the
process
Learn how to use Maya
• but we may use Maya as a rendering tool
Hone our video game or moviemaking skills
• but we will study how modern animation technology contributes
to video games and what elements of moviemaking artistry
(timing, camera angles, etc.) must reside in animation tools
Study how things move
Who else does this?
• Biomechanists
– Physics and sensors
• Artists
– Intuition and mind’s eye
Study how things move
We’ll investigate
• Human walking, running, dancing
• Bicycle riding
• Group behaviors
• Rigid body dynamics
Generate graphics that is “good
enough”
Who else studies this?
Monet
La Cathédrale de Rouen (1894)
• Perceptual psychologists
• Artists
University of
Utah
Picasso
The Bull (1946)
Generate graphics that is “good
enough”
We’ll investigate
• Recent perceptual literature (change blindness)
• Recent computer animation experiments (faking
physics)
Completing the mapping
Bridge gap between knowledge of how
things move to how they need to be
rendered
• Artists use their minds and hands
• Computer scientists use math and programs
Traditional techniques
• Keyframing (Shoemake)
– Orientation reps (quaternion, euler)
– Curve reps (linear, quadratic, wavelets)
– Interpolation (computing arclength, Gaussian
Quadrature, SLERP)
• Disney artists (Johnson)
• Timing / storyboarding
Numerical Methods
• Curve fitting (least squares)
• Optimization
– Simulated annealing (Numerical Recipes)
– Simplex
– Spacetime Constraints (Witkin & Kass)
– Genetic Algorithms (Sims)
– Neural Networks (Grzeszczuk)
Human Motion
• Motion Capture
– Retargeting (Gleicher, J. Lee, Z. Popovic, Arikan)
– Blending (Rose)
– Abstraction (Unuma)
• Walking
– Biomechanics (McMahon, Ruina)
– Gait Generation (Metaxas, van de Panne, Hodgins)
Physical Simulation
• Rigid Body
– Physics for games (Hecker)
– Featherstone’s Method
– Constraint satisfaction
• Integration
– Runge-Kutta
– Euler
• Simplification (Chenney, Lin, Popovic)
• Perception (O’Sullivan, Proffitt)
Autonomous Agents
• Behaviors (Thalmann, Badler, Blumberg)
• Group actions (Reynolds, Brogan, Helbing)
Administrivia
Syllabus
• Instructor/TA coordinates
• Prereqs
• Reading Material
• Assignments
• Grading & Honor Code
• Topic list
Instructor / TA Coordinates
Professor Brogan
• Olsson 217
– 982-2211
– dbrogan@cs.virginia.edu
– Available in office or through email appointments
Julian Dymacek
• Olsson 233
• jmd7b@cs.virginia.edu
Prerequisites
Intro to Graphics
• OpenGL skills
• User interface toolkits
• Appreciation for rendering equations
Mathematics (familiarity with…)
• Multivariate / Differential Calculus
• Probability / Statistics
• Linear Algebra
AI (familiarity with…)
Reading Material
No textbook
• Used Parent’s Computer Animation last time
– Too general
– Addresses topics I don’t care about
Lots of research papers
• I’ll provide background lectures
• Research papers provide demonstrations
Assignments
Approximately five programming
assignments
• Spacetime Constraints
• Inverse Kinematics
• Motion Capture Reuse / Retarget
• Rigid-body Dynamical Simulator
• High-level Control Systems
Assignments
Approximately four homework assignments
• Emphasize the fundamentals
– Physical simulation
– Least squares
– Simulated annealing
Assignments
Class Participation
• Due to the seminar aspect of course, participation is required
– Presentation of a paper
– Contribution to discussions
• Three questions must be submitted before class when a paper
is presented
– Graded according to: bad, good, great
– Submission questions can be skipped for excused absences
(interviews, illness, etc.)
Grading
Final scale will be set upon determination of
grad / undergrad ratio and class size
• Emphasis is on programming assignments
• There will be a final (probably no midterm)
Honor Code
Initial Assumption (assume this as default)
• All code is 100% you – no web, no other people
Relaxed Assumption
• You can use the web
Relaxed Assumption
• You can work with others
The operating assumption will be specified for
each assignment
Perception
The only reason we’re able to have this
class today is because our perceptual
system is easily tricked (but it’s finicky)
Modeling perception really matters for
computer animation
Perception
Positive afterimage (persistence of vision)
• the visual stimulus that remains after illumination
has changed or been removed
Motion blur
• Persistence of vision causes an object to appear to
be multiple places at once
Motion Blur
Virtual camera in computer graphics usually
shoots with infinitely small shutter speed
• No motion blur results
Without motion blur, 30 fps results in fast moving
objects that look like they are strobing, or
hopping
• Would CG instantaneous snapshots produce motion blur if
played at 300 fps?
What’s the rate?
Playback rate
• The number of samples displayed per second
Sample rate
• The number of different images per second
Playback
Rate
Sample Rate
TV Cartoon
30
6
TV Sitcom
30
30 (on fields)
CG Lipsync
on film
24
12
Perception
Computer graphics rendering can rely on fourhundred years of perception research by artists
• The best animators have is eighty years of Disney
In 1550, after 100 years of refining the art of
perspective drawing, artists were shocked to think
that the geometric purity of their modeled world
didn’t map to recent discoveries of the human eye.
They couldn’t even imagine how cognition affected
what one “saw.” 200 more years would pass.
Animation timeline
Persistence of vision
• Thaumotrope (1800s)
• Flipbook
• Zoetrope (1834)
• Shadow puppets
pbsKids
Animation timeline
Photography
• Muybridge (1885)
• Film projector (Edison, 1891)
Animation Timeline
First Animation
• 1896, Georges Melies, moving tables
• 1900, J. Stuart Blackton, added smoke
First celebrated cartoonist
• Winsor McCay
• Little Nemo (1911)
• Gertie the Dinosaur (1914)
Animation Timeline
1910, Bray and Hurd
• Patented translucent cels (formerly celluloid was
used, but acetate is used now) used in layers for
compositing
• Patented gray-scale drawings (cool!)
• Patented using pegs for registration (alignment) of
overlays
• Patented the use of large background drawings and
panning camera
Bray’s Studio Produced
Max Fleischer – Betty Boop
Paul Terry – Terrytoons
George Stallings – Tom and Jerry
Walter Lantz – Woody Woodpecker
1915, Fleischer patented rotoscoping
• Drawing images on cells by tracing over previously recorded
live action (MoCap)
1920, color cartoons
Disney
Advanced animation more than anyone else
• First to have sound in 1928, Steamboat Willie
• First to use storyboards
• First to attempt realism
• Invented multiplane camera
Multiplane Camera
Camera is mounted above multiple planes
Each plane holds an animation cel
Each plane can translate freely on 3 axes
What is this good for?
Zooming, moving foreground characters off camera,
parallax, prolonged shutter allows blurring some layers
(motion blur)
Stop-motion Animation
Willis O’Brien – King Kong
Ray Harryhausen – Mighty Joe Young
Nick Park – Wallace and Grommit
Tim Burton – Nightmare Before Christmas
Animation Heritage
1963 – Ivan Sutherland’s (MIT) Sketchpad
1970 – Evans and Sutherland (Utah) start
computer graphics program (and Co.)
1972 – Ed Catmull’s (Utah) animated hand
and face (later co-founded Pixar)
1970’s – Norm Badler (Penn) Center for
Modeling and Simulation
and Jack
Animation Heritage
1970’s – New York Institute of Technology
(NYIT) produced Alvy Ray Smith
(Cofounded Pixar and Lucasfilm) and
Catmull
1980’s – Daniel and Nadia MagnenantThalmann (Swiss Universities) become
European powerhouses
Animation Heritage
1980’s – z-buffer invented, SGI founded, and
Alias/Wavefront founded
1977 – Starwars
1982 – Tron (first extensive use of gfx)
1982 – Early use of particle systems (Star
Trek II: The Wrath of Khan)
1984 – The Last Starfighter (look for the
Cray X-MP in credits)
Animation Heritage
1986 – Young Sherlock Homes (first use of
synthetic character in film)
1986 – First digital wire removal (Howard the
Duck)
1988 – First digital blue screen extraction
(Willow)
The Abyss (1989) Terminator II (1991)
Casper (1995), Men in Black (1997)
Animation Heritage
ILM: Jurassic Park (1993), Jumangi (1995),
Mars Attacks (1996), Flubber (1997), Titanic
(1999)
Angel Studios: Lawnmower Man (1992)
PDI: Batman Returns (1995)
Tippett Studio: Dragonheart (1996), Starship
Troopers (1997)
Disney: Beauty and the Beast (1991), Lion
King (1994), Tarzan (1999)
Dreamworks: Antz, Prince of Egypt
Pixar: Toy Story, A Bug’s Life, Monster’s Inc.